Surfacing material and process of preparing same



Patented May 24, 1932 5 UNITED STATES PATENT OFFICE ZAN'VIL C. EOEBEL,OF NEW YORK, N. Y., ASSTGN'OR, BY MESNE ASSIGNMENTS, TO THE PATENT ANDLICENSING CORPORATION, OF BOSTON, MASSACHUSETTS, A CORPORA- TION' OFMASSACHUSETTS I SURFACIN'G MATERIAL AND PROCESS OF PREPARING SAME NoDrawing. Original application filed December 15, 1928, Serial No.326,419. Divided and this application filed March 7,

This application is a division of my coending application Serial No.326,419 filed ecember 15, 1928.

This invention relates to improvements in 5 methods of artificiallycoloring comminuted' mineral matter and particularly crushed mineral ofa character suitable for surfacing prepared roofing material. Suchgranules are usually graded to pass a six mesh screen 0 and be retainedon a thirty-five mesh screen.

Mineral surfacing atpresent employed in the asphalt roofing industrycompr ses granules obtained chiefly from slates occurring in naturaldeposits, and while these deposits vary considerably in color, thepresent demand in the industry for granules of different ,colors is notadequately satisfied by these natural deposits. In order to meet thedemand for granules of different colors, and to insure also uniformityin the supply of any given color, methods of artificially coloringgranules have been proposed.

One procedure heretofore proposed is to impregnate the granule with asoluble salt that can be transformed by heat, or by reaction with othersoluble salts into a colored owder. This procedure is objectionable,-

owever, because the colored powderlobtained by this means is quitefrangibleand readily rubs off and washes from the granule unless a.temperature sufiicient to induce incipient fusion is. resorted to. Whereheat below a and involves large consumption of fuel and considerableloss of time in carrying the granulethrough such treatment.

Another .procedure heretofore suggested is to coat the anules with drypigment and then fix the pigment on the granules by covaering the coatedgranules with a soluble silicate, such as sodium silicate, which isthereafter sub ected to a retorting operation in order tothe silicateand cause it very low cost in numerous sections of the country.

1980. Serial No. 434,179.

to bind the coloring to the surfaces of the granules. The hightemperatures necessary to insolubilize the silicate in this procedure,however, make it rather expensive to carry out the process, and inaddition, these high temperatures frequently lead to variations in thecolor of the final product unless very accurate control of thecombustion conditions is exercised. In many instances also the structureof the granule is' altered and thus the product is rendered less durablein actual use due to the effect of the high temperature treatment.

' My invention is directed particularly to improvements in methods ofthe type last referred to, and aims to overcome the disadvantagesinherent in such'methods as heretofore practiced. I have discovered thatthe in solubilization of soluble silicate for the purpose of fixingthepigment to the granules can be accomplished essentially by chemical"reaction rather than by roasting to dehydrate the silicate into aninsoluble condition, and that by the selection of certain types ofgranules as the base, this reaction may be made to take place betweenthe soluble silicate and certain constituents of the base, thus avoidingthe use of unnecessary materials and permitting the process to becarriedon at relativelylow temperatures. By thus operating I at lowtemperatures, the eifect of the oxidizing or reducing character, and ofthe intensity of the flame as a factor in the color or the product iseliminated and the liability of"injuriously affecting the structure ofthe granules is avoided.

Forthis purpose, I prefer to use crushed slag preferably basic, as thegranular base to be colored. This material afi'ords certain desirableadvantages when used as a surfacingfor prepared roofing, among thesebeing its reactive nature; its porosity and consequent low apparentspecific gravity; the roughness of its surface which enables it .tobecome securely attached to coating asphalt when the roofing, and theavailability of the base at In "accordance with my invention I effectvimbedded therein during the manufacture of,

tue of chemical interaction between the silicate" and alkaline earthconstituents of the slag material, forming insoluble complex siliicates.The reaction may be permitted-to take place at ordinaryatmospherictemperatures, or the reaction may be promoted'by heating the material.at low temperatures, but in any event, the comparatively drastic,injurious,

and costly high temperature treatment is entirely avoided in accordanceherewith.

I have produced by my invention very attractive green colored granules,the coloring being highly resistantto washing and other-- wise verylasting. This has been accomplished with the use of relatively smallamounts of green-chnomium oxide pigment. About-0.5 to 0.9% of thispigment by weight on the basis of the slag granule to be colored issuiiicient thoroughly and uniformly to coat the granules, although theamount of, pigment actually used will depend upon the shade of greendesired. The distribution of the pigmentover the surfaces of thegranules may be carried on by mixing the pigment in its dry conditionwith the dry granules but preferably the ranules, or the pigment orboth, may be slightly wetted with water to facilitate rapid and uniformcoverage.

After the granules are thoroughly and evenly covered with the pigment,the mass is then wetted with about 6% of sodium silicate and agitated tocause the silicate to coat the pigmented granules. If desired, thepigmentation of the granules may be carried on simultaneously with thesilicate treatment, by suspending the desired proportions of the pigmentin the calculated amount of the silicate, diluting with water ifnecessary, and then stirrin the granules in the suspension of pigment insilicate, until the granules are thoroughly coated with thin'films ofthe suspension.

The pigmented and silicate coated granules may then be dried at roomtemperature for say 10 to 12 hours, during which time the I silicatewill react with calcareous constituents of the granular slag base and betransformed thereby into an insolubilized compound which serves to .bindthe pigment to the granules. The reaction may be assisted, ifde'sired,by heating the coated granules in a suitable oven or in a kiln at about212 F., more or less, in which event the time required for completereaction, to take place may be reduced to a relatively short period,depending upon the degree of agitation and exposure to warm air or ases.

y my invention I have produced alsovery satisfactory red coloredgranules of various shades of pigmenting crushed slag with varyingamounts of red oxide of iron ranging from 1 to 3% and then treating thegranules with sodium .or potassium silicate which is then converted byits reaction with basis substances contained in the slag into aninsoluble condition in which state it functions to bind the pigment tothe granules.

I may also color the granules with a mixture of pigments, sayultramarine blue and yellow ochre, to obtain a resultant green whichisthen fixed to the granules by the silicate treatment as alreadydescribed.

In any event however, it will be seen that by using a reactive granuleas the base, the insoluble silicate resulting from the reaction of thesoluble silicate With'constituents of the base is an integral part ofthe granule, providing a more secure bond between the pigs, ment and thegranule than is the case where the insoluble silicate is whollyextraneous of the base. Furthermore, by providing a process ofinsolubilization ofthe silicate at low temperature, the shade of theproduct is lead acetate and then with a solution of sodium chromate, thematerials reacting to produce a yellow lead chromate, the intensity ofthe yellow depending upon the relative concentrations of the reactingsalts. The granules may then be dried in any convenient manner, and thensubjected to the silicate tiieatment for fixing the yellow pigment in pace.

Certain of the advantages of my invention may also be realized byproducingthe pigment in situ in the granules from a sin e. salt solutionintroduced into the pores of t e granules and transformed into a coloredpowder by heat treatment. For example, the slag granules may be imregnated with a solution of sodium chromate of desired concentration,the granules dried and heated to temperature say of about 1000 F. moreor less, but in any case sufiiciently high to transform the sodiumchromate to chromic oxide of desired shade of green, whereupon'thecolored granules ma be subjected to the silicate treatment atow'temperature to fix the coloring in place. i

It will be understood, that while I have specifically referred to slaggranules asthe base to be colored, the invention may be carried out andits novel features may be achieved by employing other bases which likethe sla are reactive toward thesilicate, or where t e granular materialis insufiiciently reactive. basic powders such as calcium carbonate maybe combinedwith the granules prior-to the silicate treatment.

By the expression low temperature insoluble reaction product as used inthe claims, I mean such reaction product as is formed at atmospheric orat normal drying temperatures, but in any event at temperatures notsubstantially in excess of say, 250 F.

I claim as my invention:

1. The process of producing colored anules which comprises impregnatingasic granular material with a soluble salt, converting said soluble saltin situ into a colored powder, wetting the colored granular materialwith soluble silicate and thereafter causing said silicate to react withbasic constituents of the granules whereby to form an insoluble silicate2. Theprocess of producing colored granules which comprises formingcolored powder in situ in the pores of basic granular material, treatingthe colored granular material with soluble silicate, and thereaftercausing said silicate to react with basic constituents of the granuleswhereby to form an insoluble silicate.

3. The process of producing colored granules which comprises formingcolored powder in situ in the pores of slag granules, treating thecolored granular material with soluble silicate, and thereafter causingsaid silicate to. react with constituents of the granules whereby toform an insoluble silicate.

ZANVIL C. LOEBEL.

